Began trading shrimp as a teenager, then switched to palm oil. With Kuok Khoon Hong, the nephew of longtime Malaysian billionaire Robert Kuok, bought a plantation in Sumatra that became basis of publicly traded palm oil company Wilmar International. Merged Wilmar with the senior Kuok's plantation and agribusiness group in June 2007, turning Wilmar into one of the world's largest palm oil producers. Deal boosted stock and turned Sitorus and his cofounder into billionaires.